1. Field of the Invention
This invention relates to arrangements for mounting locks and latches and, more particularly, to adapting a circular mounting hole to secure a standard D or double D lock body.
2. Description of Related Art
In the field of locks and latches, there are a great number of products that are used to secure doors, panels and cabinets in low security situations; that is, settings in which there is a need to maintain a closure against casual or incidental opening, but no requirement to resist intentional breaking and entering. A common lock for such uses is a cam lock, in which a lock armature has an arm, or cam extending radially therefrom and arranged to pivot into engagement with a fixed structural element adjacent to a cabinet door, or panel. One consummate example of a cam lock is described in U.S. patent application Ser. No. 13/889,215, filed May 7, 2013 by this inventor. The disclosure of that patent application is incorporated herein by reference. In addition, standard cam locks that are secured by threaded nuts in a mounting hole are also encompassed by this invention.
Most lock bodies are provided with a D, or double D outer configuration (hereinafter, “D/DD”) in which the mostly-cylindrical lock body has one flat side, or two opposed flat sides, respectively. These exterior features are known in the prior art, and are provided to engage a similarly formed D or double D mounting hole having a complementary configuration, so that the engagement of the flat sides in the non-circular mounting hole resists torque applied to the lock by the repeated turning of the key in the lock. In high volume manufacturing it is relatively easy to set up tooling to form a D/DD mounting hole. However, in lower volume numbers it is necessary to cut with a laser beam, water jet, or punch tool to form the D/DD opening, which can add expense to production costs. Punch cannot be used for plastic panel without fracturing the material.
One solution in the industry is to use a simply-formed circular hole, and secure the lock body therethrough with a lock nut and lock washer which are tightened to create sufficient friction to immobilize the lock body. It is a fact that many cabinets and closures are fabricated of plastic or polymer panels, and these locks are being installed through holes in such panels. It is necessary to severely tighten the lock nut to effect a secure installation, but too much compression from the lock nut may damage the plastic panel. Furthermore, lock bodies, which are often fabricated of brass or steel, are much harder that the plastic panel material, and over time the panel will wear against the harder material and the lock will loosen in its mount and begin to yield in angular turning movement when the key is rotated in the lock body.